1. Field of the Invention
Lens-casting apparatus with particular reference to improvements in casting cells of the type comprising a pair of spaced and gasketed glass mold halves.
2. Discussion of the Prior Art
Ophthalmic lens-casting cells are customarily peripherally sealed with T-gaskets, i.e. annular gaskets having a horizontally disposed generally T-shaped cross-sectional configuration. Opposite sides of internal portions of these gaskets provide seats against which, in each case, a glass mold half is clamped to form the lens-casting cavity.
Assembling a casting cell of this type requires access to both sides of the gasket and inversion or other special handling in applying the mold halves, not to mention the added tediousness of having to clamp the molds to the gasket, e.g. with a spring-tempered C-clamp.
In addition to the heretofore tedious and time-consuming assembly of parts which contributed to high end product cost and less than optimum production yield, peripheral sealing of non-spherical (aspheric or toric) mold surfaces against the gasket seats has been problematic. Variations in land or seat thicknesses are required to suit varying height or edge thicknesses of these molds. Different gasket tooling thus being required for spherical and toric lens-casting operations complicates gasket inventory and further contributes to the complexity and undue costliness of present day ophthalmic lens-casting operations.
Adding to the aforesaid problems is the customary need for enlargement of diameters of glass molds substantially beyond maximum diameters required of lenses to be cast. This is dictated by the T-gasket geometry which requires portions of the mold surfaces to make contact with gasket seats. Since difficulties in obtaining a necessary casting accuracy of toric mold surfaces are compounded by increases in mold diameter, especially in strong torics, considerable importance can be placed upon minimizing to the greatest extent possible the diametral sizes of glass-casting molds.
The latter being a special aim of the present invention is accomplished to its fullest as will become apparent hereinafter; and an additional object of the invention is to minimize the number of components necessary in gasketed lens-casting cells, to simplify and accelerate the cell assembly procedure, to enhance the accuracy of the casting surface curvature and, in general, to optimize cast lens product yield and quality with a reduction in casting apparatus cost, parts handling, inventory and overall manufacturing expenditures.
Other objects and advantages of the invention will become more readily apparent hereinafter.